Climatic tests on the housing of a wrought-iron gate

Protected in style

Scientists have been conducting building physics tests to establish whether completely encasing a listed, wrought-iron Art Nouveau gate would eliminate conditions that accelerate corrosion. The gate is currently sheltered by a glass-roofed structure made of reinforced concrete, but is still subject to heavy weathering caused by rain driven into the structure by the wind. One proposed solution is to add glass walls at the front and sides; the study aims to assess the effects this would have and make recommendations for the best way to implement it in practice.

Taking the climatic conditions of the gate without such a housing as a baseline, the researchers examined the climatic impact that completely encasing the gate would have on its immediate environment. They performed their calculations using WUFI®-Plus, a tried and tested indoor climate model developed at Fraunhofer IBP. The following questions were considered: How do different air exchange rates affect the interior climate, and what are the ideal recommendations for rates of air exchange? Particular attention was paid to relative humidity, temperature and the fluctuations in these values, with solar radiation and frost also being taken into account. The research team also examined the extent to which condensation formed on the glass panes and the gate itself. Given that condensation buildup is determined largely by the thermal transmittance of the glass used, additional calculations were made with a different U-value for the glass walls. Although the concrete cabinet around the gate was built two years ago, the scientists still had to factor residual building moisture into their measurements as the protective structure had been almost fully exposed to weathering. The new plans do not include a heating system – only a slight amount of heat will be produced by five 35-watt lamps, which will illuminate the object from the onset of dusk until midnight.

One important aspect the scientists had to consider is condensation, which can form on the inside and outside of the structure, mainly on the panes of glass and in areas where thermal bridges are created. Condensation would obstruct the view of the gate, and – much worse – could drip onto the gate and leave condensation trails on the concrete.

In summary, the scientists arrived at the following recommendations:

Completely encasing the gate is a good idea, as an all-around housing solution would provide effective protection from driving rain.

A sufficient amount of air exchange must be ensured. After encasing the gate, residual building moisture must be dried up by providing an initially higher rate of air exchange. This can be reduced once this initial phase is over, so adjustable vents are recommended.

Provided the air exchange is guaranteed through a suitable venting system, additional ventilation technology is not necessary.

If increased amounts of condensation begin to form on the inside surfaces of the housing, the rate of air exchange should be increased.